1. Field
One or more embodiments relate to an encoding apparatus and a decoding apparatus for encoding and decoding multiple channel signals, and one or more methods thereof, and more particular, to an encoding apparatus and a decoding apparatus for encoding and decoding multiple channel signals based on phase information and a residual signal, and one or more methods thereof.
2. Description of the Related Art
In general, a multi-channel audio coding may include a waveform multi-channel audio coding and a parametric multi-channel audio coding. As only examples of the waveform multi-channel audio coding, a Moving Picture Experts Group (MPEG)-2 motion compensation (MC) audio coding, an advanced audio coding (AAC) MC audio coding, a bit sliced arithmetic coding/application visualization system (BSAC/AVS) MC audio coding, and the like may be used. As only an example, a waveform multi-channel audio coding may output from a decoder five channel signals from a transmitted single or stereo encoded signal based on five channel signals input to an original encoder, noting that stereo or 7 channel signals, as well as alternative channel signal numbers, are equally available.
For example, the parametric multi-channel audio coding may include an MPEG surround coding, and output one or two input channels for representing six or eight multiple channels, e.g., after up-mixing of the transmitted one or two channels, for example.
Using an exemplary arrangement, encoding a mono or stereo signal, a parametric stereo (PS) technology may be used. Again, the parametric stereo technology may down-mix an input stereo signal to generate a mono signal, extract a stereo parameter indicating side information for the stereo signal, and encode the stereo signal by encoding the generated mono signal and the extracted stereo parameter. The decoder may then up-mix the decoded mono signal based on the decoded stereo parameter.
As examples of the stereo parameter used in this case, Inter-channel Intensity Difference (IID) or channel level differences (CLD) indicating an intensity difference based on an energy level of at least two channel signals included in the stereo signal, Inter-channel Coherence (ICC) or Inter-channel Correlation (ICC) indicating a correlation degree between two channel signals based on similarity of waveforms of the at least two channel signals included in the stereo signal, Inter-channel Phase Difference (IPD) indicating a phase difference between the at least two channel signals included in the stereo signal, Overall Phase Difference (OPD) indicating how a phase difference between the at least two channel signals is distributed based on the mono signal, and the like may be given.
Here, the parametric stereo technology may be expanded for the purpose of encoding multiple channels, i.e., plural mono or stereo signals can be hierarchically be generated and respective parameter information for each level of down-mixing can be produced. For a single layer of up-mixing, an MPEG surround technology may perform an up-mixing of an encoded mono or stereo signal to multiple channels based on a 1-to-2 (One-to-Two, OTT) module and a 2-3 (Two to Three, TTT) module, for example. As noted, and only as an example, plural such modules can be performed in a hierarchical manner, e.g., as a tree structure, so 5 or more input multiple signals can eventually be down-mixed to a single mono or stereo signal, and then eventually up-mixed into multiple signals greater than the encoded single mono or stereo signal. For example, five or seven multiple signals can be down-mixed by an encoder to one mono or stereo signal and eventually up-mixed back into the five or seven multiple signals by a decoder.
When the MPEG surround coding scheme codes the multiple channel signals by expressing the multiple channel signals with parameters, the multiple channel signals incorrectly decode all original signals from the respective parameter(s), even when a bit rate is increased, i.e., respective parameters may not provide sufficiently accurate information for an adequate decoding from a down-mixed signal(s) back into the up-mixed multiple channels signals. Therefore, the present inventors have found a desire for a method of decoding the multiple channel signals to be as close to the original signals when the multiple channel signals are expressed by parameters.